>Shouldn't that show up on the IgE/allergy test, then?  So confused!

A frequent topic, and one that is often confusing. Allergy tests can
be good indicators of an allergy (or absence thereof) , but they're
not universal indicators - not everybody who's allergic (or not)
tests positive (or negative). Statistics vary across age groups and
for other reasons.

Also, the relatively milder reactions aren't necessarily "caught" in
an allergy test. The more serious anaphylactic reactions (Type I
Immediate Hypersensitivity reactions) typically do. But an increase
in congestion, etc, may not. All of these immune system responses are
allergic in nature, but with varying degrees of severity.

My oldest son is hair-trigger allergic to milk products (and eggs and
nuts!). He tested negative in his skin and RAST tests or the first 10
years of his life, presumably because of his low level of early
exposure to milk. Yet at every ingestion, he'd have an anaphylactic
reaction. Somewhere around age ten he started to show positive skin
and RAST tests.

I say this because sometimes some of these reactions are best
indicated by the one suffering the symptoms, not necessarily the
tests. If the patient tests negative but consistently shows symptoms,
that's a possible indicator of a false negative to the test (rare, I
understand, but possible).

It can be difficult to be certain as to what food or environmental
factor triggered the symptoms; sometimes double-blind food challenges
can be used to verify the suspicion. (Neither the patient nor the
observer is aware of whether the allergen or a placebo is being fed
to the patient).

Also, dietary explorations can be used. "Trial and error" diets can
be confounding - just too many factors. Same for limited elimination
diets (one food eliminated at at time). What worked for us was a
"nothing" diet, stripping the diet back to near nothing and very
slowly introducing new food ingredients.

On the terminology:

"Intolerance" is one of those ambiguous words - it's been used by
some to describe lesser allergic responses, but that's confusing
because of the common term, lactose intolerance, for lactase
deficiency. The gastrointestinal symptoms from lactase deficiency are
not the same as those for allergic responses (although some people do
vomit and/or have diarrhea as a part of an allergic reaction). Confused?

Perhaps it's best to reserve "intolerance" for lactose intolerance or
lactase deficiency, and call the immune system responses "allergic"
responses or allergic reactions. Then one can talk about the less
severe, non-life-threatening allergic responses versus the
potentially life-threatening, severe anaphylactic reactions. Does that help?

That said, not everybody "gets" what an allergy is. Saying to a
wait-person "my child is allergic to dairy" is often totally
misunderstood. We say "allergic" they might think "gets gas" or
(worse) "doesn't like." In these circumstances, it's better to say
"my child won't be able to breath if he eats anything with milk in it
- let's see what we can do to prevent a 911 call." (Ok, off that soap-box!)

Hope that clarifies.

Mark